Light-Evoked Responses of the Mouse Retinal Pigment Epithelium

In response to light, the retinal pigment epithelium (RPE) generates a series of slow potentials that can be recorded as the c-wave, fast oscillation (FO), and light peak (LP) of the electroretinogram (ERG). As these potentials can be related to specific cellular events, they provide information about RPE function and how that may be altered by disease or experimental manipulation. In the present study we describe a noninvasive means for recording the light-evoked responses of the mouse RPE and use this to define the stimulus-response properties of the major components in three inbred strains of mice (BALBc/ByJ, C57BL/6J, and 129/SvJ) and two mouse mutants that reduce activity in the rod pathway. All of the major ERG components generated by the RPE are readily measured in the mouse. In albino strains (BALBc/ByJ and 129/SvJ) the intensity-response functions for the c-wave, FO, and LP are shifted toward lower intensities in comparison to those for C57BL/6J mice. Each of these components was markedly reduced in mice lacking transducin in which rod phototransduction is interrupted, indicating that they reflect primarily rod photoreceptor activity. All components were observed in no b-wave ( nob) mutant mice, indicating that inner retinal activity does not make a major contribution to these potentials. Further studies of mutant mice will allow us to define the functional consequences of gene manipulation on RPE function and to evaluate specific hypotheses regarding the generation of ERG components.

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Light-Evoked Responses of the Retinal Pigment Epithelium: Changes Accompanying Photoreceptor Loss in the Mouse

Journal of Neurophysiology ◽

10.1152/jn.00088.2010 ◽

2010 ◽

Vol 104 (1) ◽

pp. 391-402 ◽

Cited By ~ 24

Author(s):

Ivy S. Samuels ◽

Gwen M. Sturgill ◽

Gregory H. Grossman ◽

Mary E. Rayborn ◽

Joe G. Hollyfield ◽

...

Keyword(s):

Retinal Pigment Epithelium ◽

Structural Changes ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Retinal Disease ◽

Rod Photoreceptor ◽

Evoked Responses ◽

Photoreceptor Degeneration ◽

Rod Photoreceptors ◽

Slow Piii

Mutations in genes expressed in the retinal pigment epithelium (RPE) underlie a number of human inherited retinal disorders that manifest with photoreceptor degeneration. Because light-evoked responses of the RPE are generated secondary to rod photoreceptor activity, RPE response reductions observed in human patients or animal models may simply reflect decreased photoreceptor input. The purpose of this study was to define how the electrophysiological characteristics of the RPE change when the complement of rod photoreceptors is decreased. To measure RPE function, we used an electroretinogram (dc-ERG)-based technique. We studied a slowly progressive mouse model of photoreceptor degeneration ( Prph Rd2/+), which was crossed onto a Nyxnob background to eliminate the b-wave and most other postreceptoral ERG components. On this background, Prph Rd2/+ mice display characteristic reductions in a-wave amplitude, which parallel those in slow PIII amplitude and the loss of rod photoreceptors. At 2 and 4 mo of age, the amplitude of each dc-ERG component (c-wave, fast oscillation, light peak, and off response) was larger in Prph Rd2/+ mice than predicted by rod photoreceptor activity (RmP3) or anatomical analysis. At 4 mo of age, the RPE in Prph Rd2/+ mice showed several structural abnormalities including vacuoles and swollen, hypertrophic cells. These data demonstrate that insights into RPE function can be gained despite a loss of photoreceptors and structural changes in RPE cells and, moreover, that RPE function can be evaluated in a broader range of mouse models of human retinal disease.

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Noninvasive recording and response characteristics of the rat dc-electroretinogram

Visual Neuroscience ◽

10.1017/s0952523802196015 ◽

2002 ◽

Vol 19 (6) ◽

pp. 693-701 ◽

Cited By ~ 8

Author(s):

NEAL S. PEACHEY ◽

J. BRETT STANTON ◽

ALAN D. MARMORSTEIN

Keyword(s):

Light Exposure ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Experimental Manipulation ◽

Sprague Dawley ◽

Active Electrode ◽

Slow Potential ◽

Full Field ◽

Stimulus Response ◽

Response Characteristics

In response to light, the retinal pigment epithelium (RPE) generates a series of potentials that can be recorded using the dc-electroretinogram (dc-ERG). As these potentials can be related to specific cellular events, they provide information about RPE function and how that may be altered by disease or experimental manipulation. The purposes of the present study were to define a noninvasive means for recording the rat dc-ERG, to use this to define the stimulus–response properties of the major components, and to relate these results to measures of the rat electrooculogram (EOG). Parallel studies were conducted in two strains of rats (Long-Evans, LE; Sprague-Dawley, SD) that are commonly used in vision research. Rats were sedated with ketamine/xylazine and placed on a heating pad. Ag/AgCl wire electrodes were bridged with capillary tubes filled with Hanks balanced salt solution. The active electrode was placed in contact with the corneal surface and referenced to a second electrode placed within the orbit. The dc-ERG signal was amplified (dc-100 Hz), digitized, and stored offline. The duration of full-field flash stimuli was controlled using a mechanical shutter and flash luminance was controlled with neutral density filters. EOGs were recorded using subdermal platinum needle electrodes placed near the eye. In response to a 5-min light exposure, the dc-ERG of LE and SD rats included a distinct b-wave, after potential, c-wave, fast oscillation, and a slow potential of positive polarity the characteristics of which are consistent with a light peak.

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Ba2+ unmasks K+ modulation of the Na+-K+ pump in the frog retinal pigment epithelium.

The Journal of General Physiology ◽

10.1085/jgp.86.6.853 ◽

1985 ◽

Vol 86 (6) ◽

pp. 853-876 ◽

Cited By ~ 32

Author(s):

E R Griff ◽

Y Shirao ◽

R H Steinberg

Keyword(s):

Retinal Pigment Epithelium ◽

Channel Blocker ◽

Apical Membrane ◽

Pigment Epithelium ◽

Retinal Pigment ◽

K Channel ◽

Evoked Responses ◽

Physiological Conditions ◽

Transepithelial Potential ◽

Slow Piii

This paper presents electrophysiological evidence that small changes in [K+]o modulate the activity of the Na+-K+ pump on the apical membrane of the frog retinal pigment epithelium (RPE). This membrane also has a large relative K+ conductance so that lowering [K+]o hyperpolarizes it and therefore increases the transepithelial potential (TEP). Ba2+, a K+ channel blocker, eliminated these normal K+-evoked responses; in their place, lowering [K+]o evoked an apical depolarization and TEP decrease that were blocked by apical ouabain or strophanthidin. These data indicate that Ba2+ blocked the major K+ conductance(s) of the RPE apical membrane and unmasked a slowing of the normally hyperpolarizing electrogenic Na+-K+ pump caused by lowering [K+]o. Evidence is also presented that [K+]o modulates the pump in the isolated RPE under physiological conditions (i.e., without Ba2+). In the intact retina, light decreases subretinal [K+]o and produces the vitreal-positive c-wave of the electroretinogram (ERG) that originates primarily in the RPE from a hyperpolarization of the apical membrane and TEP increase. When Ba2+ was present in the retinal perfusate, the apical membrane depolarized in response to light and the TEP decreased so that the ERG c-wave inverted. The retinal component of the c-wave, slow PIII, was abolished by Ba2+. The effects of Ba2+ were completely reversible. We conclude that Ba2+ unmasks a slowing of the RPE Na+-K+ pump by the light-evoked decrease in [K+]o. Such a response would reduce the amplitude of the normal ERG c-wave.

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Three light-evoked responses of the retinal pigment epithelium

Vision Research ◽

10.1016/0042-6989(83)90107-4 ◽

1983 ◽

Vol 23 (11) ◽

pp. 1315-1323 ◽

Cited By ~ 50

Author(s):

Roy H. Steinberg ◽

Robert A. Linsenmeier ◽

Edwin R. Griff

Keyword(s):

Retinal Pigment Epithelium ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Evoked Responses

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Altered expression of the iron transporter Nramp1 (Slc11a1) during fetal development of the retinal pigment epithelium in microphthalmia-associated transcription factor Mitfmi and Mitfvitiligo mouse mutants

Experimental Eye Research ◽

10.1016/j.exer.2007.11.015 ◽

2008 ◽

Vol 86 (2) ◽

pp. 419-433 ◽

Cited By ~ 4

Author(s):

J. Gelineau-van Waes ◽

L. Smith ◽

M. van Waes ◽

J. Wilberding ◽

J.D. Eudy ◽

...

Keyword(s):

Transcription Factor ◽

Retinal Pigment Epithelium ◽

Fetal Development ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Altered Expression ◽

Mouse Mutants ◽

Iron Transporter

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Functional abnormalities in the retinal pigment epithelium of CFTR mutant mice

Experimental Eye Research ◽

10.1016/j.exer.2006.01.021 ◽

2006 ◽

Vol 83 (2) ◽

pp. 424-428 ◽

Cited By ~ 14

Author(s):

Jiang Wu ◽

Alan D. Marmorstein ◽

Neal S. Peachey

Keyword(s):

Retinal Pigment Epithelium ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Mutant Mice

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Pathways for the uptake and conservation of docosahexaenoic acid in photoreceptors and synapses: biochemical and autoradiographic studies

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y93-103 ◽

1993 ◽

Vol 71 (9) ◽

pp. 690-698 ◽

Cited By ~ 21

Author(s):

Nicolas G. Bazan ◽

Elena B. Rodriguez de Turco ◽

William C. Gordon

Keyword(s):

Fatty Acid ◽

Retinal Pigment Epithelium ◽

Docosahexaenoic Acid ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Photoreceptor Cells ◽

Plasma Lipoproteins ◽

Rod Photoreceptor ◽

Excitable Membranes ◽

The Central Nervous System

Docosahexaenoic acid (22:6n−3) esterified into phospholipids represents by far the most prevalent fatty acid of rod photoreceptor disc membranes and synaptic terminals. During synaptogenesis and photoreceptor biogenesis, plasma lipoproteins, secreted mainly by the liver, are the main source of plasma 22:6n−3 for the central nervous system. This systemic route (the long loop) also operates in mature animals for morphogenesis and maintenance of excitable membranes (e.g., during constant renewal of photoreceptor disc membranes). When radiolabeled 18:3n−3, the dietary precursor of 22:6n−3, is systemically supplied to 3-day-old mouse pups, it is elongated and desaturated in the liver, leading to the synthesis of 22:6n−3 – lipoproteins that shuttle the fatty acid through the bloodstream to retina and brain. When radiolabeled 22:6n−3 was used, a more efficient labeling of brain and retinal lipids was achieved. The retinal pigment epithelium is involved, not only in the uptake of 22:6n−3 from circulating lipoproteins in the choriocapillaris but also in the recycling of 22:6n−3 from degraded phagosomal phospholipids back to the inner segments of photoreceptors (the short loop), following each phagocytic event. An interplay among efficient 22:6n−6 delivery from the liver, selective uptake by retinal pigment epithelium photoreceptor cells, and avid retinal retention may contribute to the enrichment of excitable membranes of the retina with 22:6n−3 – phospholipids.Key words: docosahexaenoic acid, phospholipids, photoreceptors.

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